As many of the other reviewers have noted, Hourani's book is comprehensive in scope. Some reviewers have called it "dry as the desert." I disagree somewhat. I found Hourani's writing style smooth and comprehendible. In the end, the extensive supporting detail he provides is what tired me out. For example, in chapter 26 he wrote about the renewal of heritage in 20th century and the various forms it took in the literary world. He then goes on to give four pages of detail about various writers. So you can expect lots of supporting detail and examples. At times I found myself quickly glossing over those details of no interest to me. On the other hand, like some other reviewers, I wish the book had more depth on a few topics that interested me (early life of Muhammad, origins and nature of Sufism, Palestine/Israel issues, etc.). However, these kinds of gripes are probably to be expected, since the editorial choices and cuts of such a broad topic are so difficult to make.
The book is also very well designed. It includes an index of terms like "hadith" and "mahdi", an extensive bibliography, notes, a general index, genealogical trees, lists of dynasties, 39 BW photographs, and most importantly -- plenty of maps.
Finally, the treatment and discussion of Israel seemed dispassionate and concise.
Overall, I enjoyed the book and learned a great deal.